London-based iOS developer Six to Start details the design process behind Zombies, Run!, The Walk and Superhero Workout, and how it'll take these onto the Apple Watch.

Evading flesh-eating zombies amidst the undead apocalypse is a pretty good prompt to run like hell, no? The fear, the anxiety, and the uncertainty of what's behind – fictional as the subject may be, the reaction is one that surely all of us can agree on.

It's part of what makes Zombies, Run! (£2.49) such a successful fitness app, as the narrative-led missions pump your ears full of dialogue and interactions as you run around your neighbourhood, on a treadmill, or through any thankfully zombie-free locale you wish. Nearly a million people have snagged the app since its debut in early 2012, and developer Six to Start has significantly expanded out the original experience with many more missions and features since.

Recently, the studio put its talents to use on another fitness-centric app, Superhero Workout (£2.49), which focuses on body weight exercises you can do in your own home, but jazzes things up with comic-like scenarios. I spoke with members of the London-based team to discuss its philosophy towards improving personal fitness apps and find out what's ahead for them.

Storied sprints

Six to Start CEO and cofounder Adrian Hon took a circuitous route to become overseer of a fitness game company, first studying neuroscience and experimental psychology at Cambridge and Oxford University before joining Moshi Monsters developer Mind Candy in 2004 to work on alternate reality games. He left in 2007 to set up shop at Six to Start, and the developer has worked in recent years to provide workout motivation for folks not swayed by more traditional means.

"Our philosophy is that everyone wants to improve their health and fitness, but most people find exercising is boring, repetitive, and painful," says Adrian, with words that may sound awfully familiar to many out there. "Anything we can do to make exercise more exciting and fun is good for everyone."

"That's the key difference between us and Nike or Adidas," he continues, painting a target on a pair of corporate juggernauts. "They like to imagine that everyone wants to become a pro athlete who loves competing against their friends to run the fastest 5K or cycle the furthest; whereas we think the big problem is motivating someone to actually go out and run for 20 minutes on a rainy Sunday morning. If we can do that through story, if we can do that through gameplay, then we've done a good job."

Zombies, Run! (below) was their first attempt at doing so, and it remains the studio's best-known work, putting you in the role of Runner 5 as you leave your refugee compound in search of supplies. As you run, the iOS and Android app monitors your progress and pushes the story forward accordingly, wrapping you up in the tense tale of a daring courier amidst a horrifying setting. What began with about 30 playable missions following a successful Kickstarter campaign has now blossomed into an expansive experience with about 200 total missions.

Six to Start co-created the game with author Naomi Alderman, who over lunch in early 2011 shared with Adrian that she'd joined an online running group. One fellow member apparently claimed to have joined to get in shape "to survive the zombie apocalypse," and the offhand comment sent their minds sprinting.

"To be honest, I was kind of sick of zombies at that point – it felt like every game and movie was about zombies – but the more we talked about it, the more we realized that a zombie running game made a heck of a lot of sense," Adrian says. "It explained why you could never jump in a car, why you would repeatedly put yourself into danger, or why you'd need to go and collect supplies."

Most importantly, the unique setting, well-tuned pacing, and smart writing helped motivate people who had previously failed to stick to running routines, or had never seriously run before in their lives. Add in gaming elements like the between-run base builder, racing missions, and social functionality via the web, and Zombies, Run! can potentially fuel hundreds of hours of running. You get all that from an audio drama about the undead.

Its success also caught the attention of the NHS and Department of Health, which last year funded The Walk, (below) another mobile app co-created by Six to Start and Alderman. Focused on rewarding players who choose to spend more time on their feet during the day, it again used narrative (this time with a sci-fi theme and an intriguing conspiracy) to encourage movement from those perhaps not likely to find dedicated chunks of time to work out.

Zero to Hero

This August, Six to Start shifted away from cardio and launched a brand new kind of fitness app, Superhero Workout (below). Like the company's previous apps, there's a thematic hook here: you'll take on missions and complete body weight reps by performing special moves, like punching the air to deflect virtual missiles and doing crunches to charge up a generator.

"Having the player piloting AEGIS One (our experimental exo-suit) gave us lots of fun technobabble reasons for the player's actions," explains Matt Wieteska, lead writer and audio director for Superhero Workout. "You aren't just doing burpees, you're charging your main plasma cannon!"

Adrian says he was inspired by "seven-minute workout" apps that he felt weren't doing enough for users. "I see the appeal, but I also found myself getting bored after a couple of weeks, and not really knowing if I was improving my performance," he claims. "I also had the sneaking suspicion that seven minutes of working out – even if it was high intensity – wasn't likely to do much to my fitness. As it turns out, seven minutes really isn't enough: the research shows that you're meant to do two or three times that amount."

Whereas an app like Zombies, Run! is meant to spur on your workout without the device ever leaving your pocket, Superhero Workout has you prop up your iPhone or iPad so you can see the screen – and so that the front camera can see you too. As you perform the exercises and follow the action-packed prompts, the camera tracks your reps and calories burned, both so you're informed and so that the app can keep you engaged as it rolls on to the next set of workouts. That last part also provided a unique test for the team.

"Each set of reps is only 30 seconds long, and the player is changing exercises after each set. This means we need to re-contextualize what the player is doing every 30 seconds," explains Wieteska. "This forces a really rapid pace on to the story, which is exciting but also pretty challenging! We found ourselves having to find a lot more individual action beats than you'd normally need for every beat of story, simply because the pace of the exercises meant the action needed to move so quickly."

But while very different in tone and fitness target than Six to Start's previous efforts, Superhero Workout provides another effective, immersive workout experience that draws players in with narrative and context, but ultimately gives them stellar results.

And Six to Start certainly isn't done in this category, as Adrian says another distinct fitness experience is just around the corner: "We have another fitness game coming out later this year that's quite different from our previous games – this one is aimed at all ages, including children – so that will be exciting."

Fitness apps for the Apple Watch

Adrian admits that they're interested in pursuing non-fitness games, as well, but adds that they "want to reach out to an ever broader audience" with Zombies, Run! as it approaches a million total users. A fourth season of missions for the app will launch in 2015, but Six to Start is also working on support for the Apple Watch. Apple hasn't provided developers an SDK just yet, but the studio is investigating all of the ways (large and small) that they can utilize that next big gadget.

"There are some easy things we can do, like adding notifications and run information to the watch screen; and there are more complex things like adding interactivity to the runs," he says. "We have to be careful about doing that, because I don't think runners want to be stopping every three minutes to fiddle with their watch, but there will be some specific interactions we can add that should improve the experience."

Luckily, Six to Start has been considering such options for Zombies, Run! for much longer than the last few weeks, so once Apple is ready to starting bringing third-party developers onboard to create Watch-centric apps, they will be too. "We've been thinking about making wearable games for many years now," Adrian asserts, "and we have plenty of ideas about how to make Zombies, Run! more exciting."